The conventional CRT is a ubiquitous device that is used to display images in a variety of instruments. The CRT includes a cathode as an electron source. The cathode is heated, which causes it to emit a cloud of low-energy electrons. Focusing electrodes narrow this cloud into a beam, control electrodes ensure that the beam flows through the device at an appropriate rate, and accelerating electrodes accelerate the electrons to the requisite energy level (about 500 eV to 1500 eV for low-voltage phosphor screens). The cathode and the accompanying electrodes described above are together commonly referred to as an "electron gun." The beam of electrons then strikes a phosphor-coated screen, which causes the phosphor to emit light. This light produces coherent images because the electrons are appropriately deflected by deflecting electrodes before they strike the screen.
Deflection of the electron beam is effected by two sets of orthogonal deflectors; one that deflects the beam horizontally, and one that deflects the beam vertically. The angle of deflection that can be achieved is proportional to the voltage applied to the deflecting electrodes and inversely proportional to the energy of the beam. For a more detailed discussion of CRT technology, see, e.g., Robert A. Meyers, ed., Encyclopedia of Physical Science and Technology, Second Edition, Vol. 5, pp. 695-701, Academic Press (San Diego, Cailf., 1992) and Jerry C. Whitaker, ed., The Electronics Handbook, pp. 367-386, CRC Press, Inc. (Beaverton, Oreg., 1996).
For all of its success as a display device, the CRT has significant limitations in terms of power consumption, cost and size. The electron-producing cathode is a high-voltage, high-power device that nonetheless emits electrons in a diffuse cloud with low energy. The electron cloud must be focused and accelerated into a fast, tight beam to be useful. This requires the use of focusing electrodes as well as accelerating electrodes, both of which, but especially the latter, contribute to the high-energy consumption of the CRT. In addition, a long CRT tube is necessary to take advantage of the deflection angle imparted by deflection electrodes (a longer tube means that the electrons will be deflected a greater absolute distance). This problem can be off-set by an increase in the voltage of the deflecting electrodes, but this of course is not an ideal alternative.
Because of these and other limitations, there is a need in the art for an alternative to conventional CRT displays.